Japanese Patent Application No. 2001-20703, filed Jan. 29, 2001, is hereby incorporated by reference in its entirety.
The present invention relates to a power supply apparatus that reduces its own current consumption at the time of a light load to thereby eliminate power wastage, to thereby improve an overall power conversion efficiency thereof.
Conventionally, for example, charge pump DC/DC converters and switching regulators are known as power supply apparatuses.
A charge pump DC/DC converter uses charge and discharge of a capacitor to convert an input voltage to a given output voltage.
A switching regulator switches an input voltage and converts the input voltage to a given output voltage.
However, since a charge pump DC/DC converter is designed taking in account of the maximum load for its operation, its own current consumption is the same even when a load condition changes. Therefore, it does not waste the power at the time of a heavy load, but it is inconvenient that its capacity becomes excessive at the time of a light load such that the power is wasted, and the overall power conversion efficiency is lowered.
On the other hand, a switching regulator has a large current consumption but a high power convention efficiency. Accordingly, its high power conversion efficiency is effective at the time of a heavy load. However, it is inconvenient that the overall power conversion efficiency is lowered because its own current consumption is large at the time of a light load.
In view of the above, the present invention may provide a power supply apparatus that reduces its own current consumption at the time of a light load, to thereby improve an overall power conversion efficiency thereof.
One aspect of the present invention relates to a power supply apparatus comprising: an input terminal; an output terminal; a charge pump DC/DC converter provided between the input terminal and the output terminal; and a series regulator connected in parallel with the charge pump DC/DC converter between the input terminal and the output terminal, wherein the charge pump DC/DC converter and the series regulator are selectively operated according to size of a load connected to the output terminal.
In this manner, in accordance with this aspect of the present invention, a charge pump DC/DC converter and a series regulator having different characteristics are combined, and the DC/DC converter and the series regulator are selectively operated according to size of a load to take out an output voltage on an operation side thereof.
More concretely, at the time of a heavy load, the DC/DC converter is operated. Although the DC/DC converter has a large current consumption of its own, it has a high conversion efficiency of an output power with respect to an input power. Accordingly, since a load current increases at the time of a heavy load, it is effective to use the DC/DC converter the power conversion efficiency of which is high, and its current consumption can be neglected since the load current is large.
On the other hand, at the time of a light load, the series regulator is operated. Although the series regulator has a small current consumption of its own, it has a low power conversion efficiency. Accordingly, at the time of a light load, when the series regulator is used, its low power conversion efficiency can be neglected because its current consumption is small.
Accordingly, since its current consumption can be lowered at the time of a light load compared to that at the time of a heavy load, the power conversion efficiency as a whole can be improved when it is used both at a heavy load and a light load.
Another aspect of the present invention relates to a power supply apparatus comprising: an input terminal; an output terminal; a switching regulator provided between the input terminal and the output terminal; and a series regulator connected in parallel with the switching regulator between the input terminal and the output terminal, wherein the switching regulator and the series regulator are selectively operated according to size of a load connected to the output terminal.
In this manner, in accordance with this aspect of the present invention, a switching regulator and a series regulator having different characteristics are combined, and the switching regulator and the series regulator are selectively operated according to size of a load to take out an output voltage on an operation side thereof.
More concretely, when the load is heavy, the switching regulator is operated. Although the switching regulator has a large current consumption of its own, it has a high conversion efficiency of an output power with respect to an input power. Accordingly, since a load current increases at the time of a heavy load, it is effective to use the switching regulator the power conversion efficiency of which is high, and its current consumption can be neglected since the load current is large.
On the other hand, at the time of a light load, the series regulator is operated. Although the series regulator has a small current consumption of its own, it has a low power conversion efficiency. Accordingly, at the time of a light load, when the series regulator is used, its low power conversion efficiency can be neglected because its current consumption is small.
Accordingly, since its current consumption can be reduced at the time of a light load compared to that at the time of a heavy load, the power conversion efficiency as a whole can be improved when it is used both at heavy load and light load.